The present invention relates to a medical prosthesis for the replacement of at least a portion of a naturally occurring vertebra. More particularly, the invention relates to a prosthesis for the replacement of an injured, diseased or otherwise malfunctioning vertebra which prosthesis has the ability of functioning, at least in part, as a naturally occurring vertebra.
One of human kind's major medical problems involves various difficulties with the back. In particular, back concerns may involve one or more vertebrae which are cushioned by discs positioned between the individual vertebrae. The vertebrae together function as a main component of the back bone, and together with the discs and spinal cord form the spinal column. Another important function of the vertebrae is to protect the spinal cord from injury. Individual vertebrae each include a hole through which the spinal cord passes.
Because of exertion, injury, illness, accident or abuse, one or more of the vertebrae and/or one or more discs may become damaged and/or not function properly. Minor problems of this type can be treated with medication and other non-invasive therapy. However, it is often necessary to remove at least a portion of the damaged and/or malfunctioning component or components of the spinal column. For example, when a disc becomes ruptured, the ruptured disc may be surgically removed and the two vertebrae from between which the disc is removed are fused together. This fusing results in a loss of flexibility since the two fused vertebrae are substantially inflexible relative to each other.
This problem with inflexibility is even more severe if a damaged vertebra is to be removed. For example, see Doty U.S. Pat. No. 4,599,086, and Ogilvie, et al U.S. Pat. No. 4,636,217. In each of these patented systems only a portion of the damaged vertebra is removed and replaced by an assembly which does not resemble the removed naturally occurring vertebra, and which is secured directly to the adjacent vertebrae on both sides of the damaged vertebra. Thus, using these systems there are three (3) vertebra spaces that are inflexible relative to each other.
Clearly it would be advantageous to provide a vertebra/disc replacement system which overcomes or at least reduces the severity of one or more of these problems, in particular the flexibility problems noted above.